Magnesium-base alloy



Patented Jan. 3, 1961 0.2 to 2 percent of manganese are alloyed with magnesium and suflicient zirconium is added to more or less saturate 2 967 104 the alloy while molten, this amount being from about 0.001 to 0.15 percent depending on the manganese con- MAGNESIUM-BASE ALLOY tent. That is, at the lower end of the range of the mani ganese content larger amounts of zirconium can be tolg fi q efg g" g i 1353: erated, as up to 0.15 percent when the manganese of ggfig I an a corpo content is 0.2 percent; and at the higher end of the range of manganese content, the smaller the amount No Drawing. Filed June 5, 1957, Ser.No. 663,601 of the zirconium that can be tolerated, as 0.001 percent zirconium when the manganese content is 2 percent. The 4 Claims (CL 75-168) preferred range of proportions of the alloying constituents are from 1.5 to 3.5 percent of thorium, 0.4 to 1.0 percent of manganese, and from 0.001 to 0.05 percent The invention relates to magnesium-base alloys. It 5 of zirconium, the balance being magnesium except for more particularly concerns magnesium-base alloys conincidental impurities which may be present in the metals taining both thorium and manganese and having among used. Usually the total amount of incidental impurities other desirable properties high creep strength and rolla does not exceed 0.3 percent of the weight of the alloy. bility. A specific alloy composition having general application The desirable property of lightness in weight of magwithin the scope of the invention is one composed of nesium is of little value in stressed parts because of its 2.0 percent of thorium, 0.6 percent of manganese, and relatively low tensile strength especially at more or less 0.01 percent of zirconium, the balance being magnesium. elevated temperatures. Attempts to produce alloys hav- The order in which the metals are alloyed does not ing magnesium as a base that are light and not only appear to be critical. It is generally preferable to first possess high strength at more or lesselevated temperamelt the magnesium required as in a steel pot with a suittures but also are capable of being rolled readily into able saline flux for magnesium, such as one composed of sheets and plates have met many difllculties. Among the 50 parts of potassium chloride, parts of barium chlo magnesium-base alloys having good creep resistance is ride, 15 parts of magnesium chloride, 5 parts of calcium the ternary alloy of magnesium, thorium, and manganese fluoride. Following the melting of the magnesium, the disclosed in US. Patent 2,774,664. This alloy contains requisite amounts of the other metals are added. The from 0.5 to 8 percent of thorium and from 0.2 to 2 melt is stirred for as long as 10 to 20 minutes to ensure percent of manganese. Although it is possible to roll solution of the alloying metals in the molten magnesium. this alloy into sheet and plate, this is diiiicult and waste- After the alloying is completed as described, a suitable ful of metal because the metal during rolling cracks at r saline refining flux may be added such as one composed the edges entailing waste. The rolling difllClllty is due in o 95 P e Of barium chluride and 5 percent of cab part at least to the low malleability of the alloy. Accord- Clunl fiuonfle and melt Stirrei The fluXed melt ing to the present invention, this difficulty is reduced if obtauledi elther Wlth Wlthout h l the Iefimng not entirely overcome by appropriate additions of zirfl allowed, to settlexby holdmg 1t qulescent for f conium time, e.g. 20 minutes. 'lhe supernatant molten alloy 1s The invention then is based upon the discovery that decanted or otherwlse Separated from. the fl and the magnesium-base magnesinm-manganesethorium terfrom the pot as desired? Cast 9 a smtable mold is generally preferable 1n prepanng the alloy for i E 1noy t1er ateS the mcluswn of Small amounts, rolling to cast the metal into ingot before rolling into zlrcomum m splte of the presence of mallganese Yvhlch sheet. In the rolling reductions in thickness of up to 20 has been taught heretofore to prevent effective alloying of percent per pass may be made. zlrcomum magflesmm'base alloys wmamms P The following tabulation of alloys made in accordance nese. In this lnventron but a small amount of Zll'COIllllm i the fg egoing method is illustrative of the hwen. is required, an amount which is tolerable in spite of the i I h cxampies f T l I the Specimens were Presence of manganese. rolled from east ingot heated to about 900 F.

Table 1 Alloy Properties 1 Composition, Bal. Mg F 400 F. 600 F. No.

Per- Per- Per- Per- Per- .5% Per- .5% cent cent: cent cent; TYS CYS TS cent 'IYS TS EX cent; TYS TS EX Th Mn Zr E E E 2.3 0.0 0.01 7 26 25 35 13 20 24 12 19 12 15 4.2 2.6 0.5 0.04 7 27 24 35 15 21 24 13 25 11 15 4 2.7 0.44 0.05 0 2s 2s 35 17 20 22 11 -10 0 1a 3.6 2.8 0.18 0.15 10 2s 24 34 20 20 22 7.3 78 5 11 0.6 2.0 0.09 0.49 7 2s 25 35 17 21 23 02 0 11 0.8

1 Sheet rolled from east ingot at 900 F. Stress in 1000s p.s.i. strength, were measured at 0.2% deviation from the modulus lino.

All specimens have equiaxcd grain structure. .5% EX: In this column is in hours.

In carrying out the invention in its broadest aspects from 0.5 to 8 percent by weight of thorium and from TYS, the tensile yield strength and CYS, the compression yield given the load in 1000s of p.s.i. at which the specimen exhibits atotal extension of .5 percent in length The alloy may be extruded readily at suitably elevated temperature and exhibits desirable mechanical properties especially increased ductility as shown in the comparative data in Table II of an alloy prepared in accordance with the invention and a related parent ternary alloy for comparison.

2. A magnesium-base alloy containing from 1.5 to 3.5 percent of thorium, 0.4 to 1.0 percent of manganese, and from 0.01 to 0.05 percent of zirconium, the balance being magnesium.

Table 11 Alloy Extrusion Conditions Properties 1 Composition Grain Temp., Speed, Rcduc- PC!- No. Type F. it./n1in. tion in cent; TSY CYS 'JS Percent Percent Percent area E Th Mn Zr 3. 2 1. 6 0. 003 E 800 90 :1 10 40 32 44 Blank-.- 3. 4 1. 7 C 800 5 00:1 1 38 30 44 E=equiaxed grain structure; O=columnar grain structure; TYS and OYS means tensile yield strength and compression yield strength, respectively, at 0.2% deviation from the modulus line.

1 Stress in 1000s p.s.i.

Among the advantages of the invention are that the alloy resists work hardening so that a substantial amount of cold working is possible without excessive work hardening; the alloy resists surface and edge cracking during rolling so that large thickness reductions per pass are possible, thereby saving rolling time and avoiding waste of metal; the alloy resists tearing during extrusion as on die expressing objects, such as bars, tubing, angles, etc., as a result a desirable surface is exhibited on extruded shapes especially those produced at the low temperatures 3. A magnesium-base alloy containing 2.0 percent of thorium, 0.6 percent of manganese, 0.01 percent of zirconium, the balance being magnesium.

4. A magnesium-base alloy consisting of 0.5% to 8.0% thorium, 0.2% to 1.0% manganese, 0.05% to 0.15% zirconium, the balance being magnesium.

References Cited in the file of this patent UNITED STATES PATENTS at which maximum mechanical properties are obtained. 2,774,654 Mcponald 18, 1956 1 l i 2,788,272 Whitehead et a1. Apr. 9, 1957 1. A magnesium-base alloy containing from 0.5 to 8 percent of thorium, 0.2 to 2.0 percent of manganese, FOREIGN PATENTS and from 0.001 to 0.15 percent of zirconium, the balance 511,137 Great Britain Aug. 9, 1939 being magnesium. 591,225 Great Britain Aug. 12, 1947 

1. A MAGNESIUM-BASE ALLOY CONTAINING FROM 0.5 TO 8 PERCENT OF THORIUM, 0.2 TO 2.0 PERCENT OF MANGANESE, AND FROM 0.001 TO 0.15 PERCENT OF ZIRCONIUM, THE BALANCE BEING MAGNESIUM. 